Cobalt-rich ferromanganese crusts:
They are formed as manganese and iron precipitate in cold seawater and get deposited in layers of up to 25 centimetres thick. They can meet up to 20 per cent of the global cobalt demand. These crusts hold rare earth elements. These crusts, attached to surfaces of seamounts, ridges and plateaus, were first targeted for exploration by International Seabed Authority. Most of them are in the Pacific Ocean, east of Japan and the Mariana islands.